GB2174801A - Determination of gasborne fibres - Google Patents
Determination of gasborne fibres Download PDFInfo
- Publication number
- GB2174801A GB2174801A GB08511883A GB8511883A GB2174801A GB 2174801 A GB2174801 A GB 2174801A GB 08511883 A GB08511883 A GB 08511883A GB 8511883 A GB8511883 A GB 8511883A GB 2174801 A GB2174801 A GB 2174801A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- infra
- zone
- particle
- fibre
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002245 particle Substances 0.000 claims abstract description 34
- 239000000835 fiber Substances 0.000 claims abstract description 21
- 239000000428 dust Substances 0.000 claims abstract description 18
- 230000005855 radiation Effects 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- URAYPUMNDPQOKB-UHFFFAOYSA-N triacetin Chemical compound CC(=O)OCC(OC(C)=O)COC(C)=O URAYPUMNDPQOKB-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005183 environmental health Effects 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 235000013773 glyceryl triacetate Nutrition 0.000 description 1
- 239000001087 glyceryl triacetate Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 231100000206 health hazard Toxicity 0.000 description 1
- 238000000399 optical microscopy Methods 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 229960002622 triacetin Drugs 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
Landscapes
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Dispersion Chemistry (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
An apparatus for determining gasborne fibre concentration has a heating zone (1) for a sample of gas containing dust. A laser beam (9) heats each dust particle before the gas sample enters a transport zone (4) having two infra-red radiation detectors (6, 7). The signals from the detectors are compared at 10 to detect the loss of temperature associated with the larger surface area of a fibre compared to a normal dust particle. <IMAGE>
Description
SPECIFICATION
Determination of airborne fibres
This invention concerns a method of determining airborne fibres, especially in the presence of nonfibrous dust.
It has become increasingly important to determine the concentration of airborne fibres, as environmental health hazards become widely appreciated. Particularly toxic fibres, such as asbestos fibres, are determined by the internationally-accepted "Membrane Filter Method", in which dust-laden air is drawn through a membrane so that fibres and other dust particles are collected on its surface. The filter is then mounted on a glass slide and made transparent by, e.g. acetone vapour and triacetin, and the deposit is evaluated by optical microscopy. This method is labour intensive, delays are experienced, and the results are influenced by the human factor. Several attempts have been produced automated filter counters, but these have been suffered from high costs, lack of accuracy or unreliability, and inconvenience.
The present invention provides a method of determining gasborne fibre concentrations comprising subjecting a sample of gas containing dust to heating, passing gas containing heated dust particles past a first infra-red radiation detector and detecting a first emission for each particle, passing the gas a second infra-red radiation detector positioned remote from said first detector, and assessing a second emission for each particle, comparing the first and second emissions and determining a value representative of the fibre content of the gas.
The invention also provides an apparatus for determining gasborne fibre concentration, comprising a gas sample treatment zone, a heat source capable of heating each gasborne dust particle in said zone, a transport zone connected to said treatment zone and spaced apart first and second infra-red radiation detectors each capable of measuring an emission for each particle as it passes through said transport zone, and means for comparing the measured emissions from said first and second detectors and for deriving a value representative of the fibre content of the gas, and means for drawing a sample of gas containing particles through said treatment zone and past said first and second detectors.
One possible method of heating the gasborne dust particles is to treat the sample of gas containing gasborne dust with a infra-red radiation eg from a laser operating at an infra-red frequency.
Suitable lasers are commercially available and include solid state and gas lasers; a continuous output carbon dioxide laser is preferred. The particles require to be heated to a temperature such that the second detector can discriminate the infra-red signal from individual particles amongst the noise.
Other heating means such as electric coils and gas flames, may be less expensive or offer other advantages such as miniaturisation.
Suitable infra-red radiation detection systems incorporate a photomultiplier or any other device capable of rapid response to fast-moving particles yielding relatively low-level infra-red signals.
Preferably, gas sampling is done continuously, and preferably the gas passes through an elongated heating zone, the flow rate and dimensions of which are such that all particles have been uniformly heated by the time they pass into the transport zone. The particles are not subjected to further heating in the transport zone, and hence begin to radiate heat. A fibre has a greater surface area than a more compact particle of equivalent mass, and will emit more heat at a given temperature; this will generally be read by the first detector as being equivalent to the emission from a larger compact particle. Because of the larger surface, the fibre will lose heat more quickly than a more compact particle of the same mass, and hence the second detector will detect a lower heat emission for the fibre.The first and second detector signals are suitably combined to give a ratio, and the ratio for a fibre will therefore be larger than for a compact particle. A value for the fibre content of the gas may therefore be calculated using known means such as a microprocessor.
The identification of the particle at the second detector is achieved by choosing suitable gas flow rates and apparatus dimensions, so that for the expected fibre concentration, the probability of that particle and no other particle arriving at the second detector at the expected time is high.
The invention will now be described by way of illustration, with reference to the accompanying schematic diagram.
Gas containing dust particles is drawn (gas flow is indicated by arrows) into a imm diameter bore, 1, in a block of aluminium, 2, by means of a pump (not shown) connected to an outlet, 3. The pump suitably provides a flow rate of 200ml/min. An additional bore, 4, is drilled at right angles to bore 1 and is of 2mm diameter. A filter, 5, is positioned at the end of the additional bore before the outlet, to remove all dust particles over 1 micron in size. The filter may provide additional information on the dust, if desired. First and second photomultipliertype infra-red detectors, 6 and 7, are mounted 30mm apart in the block so that they see the entire cross-section of bore 4 through windows, 8.In this particular prototype form, the source of heat is a continuous output carbon dioxide laser (not shown) which produced a beam, 9, or IR radiation of 10.6 micron wavelength which completely traverses the bore, 1, which constitutes the treatment zone of the present invention. All the dust particles in the gas are heated in the zone to 1,280"C, before they pass into bore, 4, which constitutes the transport zone of the present invention. The detectors 6 and 7 produce a signal for each particle which is fed to a microprocessor, 10, which calculates the ratio of the signals and a "fibre" or "non-fibre" allocation is made for each particle. The microprocessor desirably produces an average and total "fibre' count over the sampling time, and these counts may be stored or displayed continuously.
The dimensions of the above-described device are small in relation to those of automated fibre counters based upon alternative principles and this provides for the possibility that with suitably compact heating means, such as a small electric coil, and suitably small radiation detectors, such as silicon or germanium photocells, a personal sampler fibre detector capable of being carried on the body of a user, can be constructed.
Claims (9)
1. A method of determining gasborne fibre concentrations, comprising subjecting a sample of gas containing dust to heating, passing gas containing head dust particles past a first infra-red radiation detector and measuring a first emission for each particle, passing the gas past a second infra-red radiation detector positioned remote from said first detector, and measuring a second emission for each particle, comparing the first and second emissions and determining a value representative of the fibre content of the gas.
2. A method according to claim 1, wherein the gas is heated by a laser operating at an infra-red frequency.
3. A method according to claim 1 or 2, wherein gas sampling is carried out continuously, the gas sample passes firstly through an elongate heating zone and secondly through a transport zone in which said first and second radiation detectors are positioned.
4. A method according to claim 1, substantially as hereinbefore described.
5. An apparatus for determining gasborne fibre concentration, comprising a gas sample treatment zone, a heat source capable of heating each gasborne dust particle in said zone, a transport zone connected to said treatment zone and spaced apart first and second infra-red radiation detectors each capable of measuring an emission for each particle as it passes through said transport zone, and means for comparing the measured emissions from said first and second detectors and for deriving a value representative of the fibre content of the gas, and means for drawing a sample of gas containing particles through said treatment zone and past said first and second detectors.
6. An apparatus according to claim 5, wherein the heat source is a laser operating at an infra-red frequency.
7. An apparatus according to claim 6, wherein the laser is a continuous output carbon dioxide laser.
8. An apparatus according to any one of claims 5 to 7, comprising also a filter to collect all dust particles greater than 1 micron diameter downstream of the second detector.
9. An apparatus according to claim 5, substantially as hereinbefore described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08511883A GB2174801B (en) | 1985-05-10 | 1985-05-10 | Determination of gasborne fibre concentrations |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08511883A GB2174801B (en) | 1985-05-10 | 1985-05-10 | Determination of gasborne fibre concentrations |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8511883D0 GB8511883D0 (en) | 1985-06-19 |
| GB2174801A true GB2174801A (en) | 1986-11-12 |
| GB2174801B GB2174801B (en) | 1988-06-15 |
Family
ID=10578941
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08511883A Expired GB2174801B (en) | 1985-05-10 | 1985-05-10 | Determination of gasborne fibre concentrations |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2174801B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0310348A2 (en) * | 1987-09-30 | 1989-04-05 | Btg International Limited | Method and apparatus for the measurement of airborne fibres |
| DE4433837A1 (en) * | 1994-09-22 | 1996-03-28 | Guenter Prof Dr Struebel | Safe, rapid qualitative determn. of asbestos fibres with little appts. |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105424566A (en) * | 2014-11-10 | 2016-03-23 | 北京至感传感器技术研究院有限公司 | Dust particle detection device |
| CN108593416B (en) * | 2018-04-08 | 2020-09-08 | 国家纳米科学中心 | Micro-nano particle detection system and method |
-
1985
- 1985-05-10 GB GB08511883A patent/GB2174801B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0310348A2 (en) * | 1987-09-30 | 1989-04-05 | Btg International Limited | Method and apparatus for the measurement of airborne fibres |
| EP0310348A3 (en) * | 1987-09-30 | 1990-01-10 | National Research Development Corporation | Method and apparatus for the measurement of airborne fibres |
| DE4433837A1 (en) * | 1994-09-22 | 1996-03-28 | Guenter Prof Dr Struebel | Safe, rapid qualitative determn. of asbestos fibres with little appts. |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2174801B (en) | 1988-06-15 |
| GB8511883D0 (en) | 1985-06-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |